Plants from Cichorium intybus L species adapted to forcing culture, also called endives or witloof chicory, are widely grown throughout Europe and temperate areas in Asia. It is a very branchy plant, with stiff branches being spaced apart from one another. The lower leaves are usually divided, with lobes or segments arranged on both sides, spaced apart and often inverted, with an end lobe; the top leaves are entire, encompassing the stem with their base, and the higher leaves are reduced to relatively small bracts. The root parenchymal cells produce holosides (starch, inulin, etc) from substances originating from green organs where they have been synthesized. During the growth phase, roots constantly bulge out as a result of hyperplasia of their parenchymae, with holosides accumulating therein, so as to form tuberous roots.
The ability of the Cichorium intybus L species, and more specifically of some varieties of such a species, such as the Witloof type varieties, to produce tuberous roots makes such plants adapted to being grown in the dark through forcing culture. The cultivation, for a 21 day forcing, comprises growing endives in tubs containing a nutrient solution brought to a temperature from about 18° C. to about 21° C. and an air temperature of about 1° C. to 3° C. lower than the nutrient solution temperature. Endives are grown through forcing in the dark so as to cause the leaves to wilt in order to produce essentially white mature plants with the outer edge of the leaves only having a slight yellow color.
Producing endives through forcing traditionally occurs at a large scale in rooms where tubs are stacked wherein endive roots are immersed in a nutrient solution, under dark conditions, under solution and room temperature conditions, and under accurately controlled hygrometry conditions. Thus, forcing cultivation of endive requires significant financial investments both in equipment and labor in order to achieve the various respective steps of sowing, root harvesting, and their forcing in a cultivation room, in order to produce endives at a large scale.
Cultivating endives through forcing is intended to produce chicories that will be marketed. Chicories are essentially made of leaves wilting in the dark, originating from the root neck. Forcing cycles are subjected to highly accurate and planned cultivation conditions, cycles and schedules so as to optimize the production costs.
In order to make available for the consumers a novel and varied range of plants derived from endive, able to be marketed at reasonable costs, it is required that the novel plants should be adapted to the production conditions being traditionally used for the endive. Indeed, new industrial investments that should be specifically adapted to the production of new plants of the Cichorium species would not be economically compatible with the market. Any new variety intended to be produced through forcing should, consequently, be able to integrate in the production system already developed for the endive.
The witloof chicory type Cichorium intybus L is an important and valuable vegetable crop. Thus, a continuing goal of witloof chicory plant breeders is to develop stable, high yielding witloof chicory cultivars that are agronomically sound. The reasons for this goal are obviously to maximize the amount of yield produced. To accomplish this goal, the witloof chicory breeder must select and develop witloof chicory plants that have traits that result in superior cultivars.